Coca-Cola Amatil owns softdrink production and distribution for Australia and Papua New Guinea.
Dublin-based Setanta Asset Management said CCEP's offer, which valued CCA at around $9.3 billion, was opportunistic and the offer price - which would be reduced if Amatil declared a dividend - materially undervalued the business.
The Australian Financial review reports that Setanta urged Amatil to engage with CCEP to secure a better price for the company's independent shareholders.
"The offer from CCEP fails to take into account the successful transformation program that is already under way in [Amatil's] Australian beverages division, in addition to the strength of the business in New Zealand and growth potential in Indonesia," said Fergal Sarsfield, Setanta senior portfolio manager.
"Amatil's management team have worked tirelessly to develop the company and the offer of $12.75 per share does not reflect the strength and value of the business.
"We believe CCEP are acutely aware of both the transformation that Amatil has undertaken and the growth opportunities that lie ahead and are being very opportunistic in attempting to take over the company at this time," Sarsfield said.